Highly selective in-situ generation of 1O2 via electronic structure regulation of single atom sites in electro-Fenton system

Highly selective generation of singlet oxygen ( 1 O 2 ) in the electro-Fenton system remains challenging due to susceptibility of the O-O bond to break in O 2 reduction reaction and activation process of H 2 O 2 . Herein, the nitrogen-coordinated Fe single-atom catalyst with a high coordination number (FeN 6 /CN) was synthesized, allowing the Fe sites to remain trivalent while presenting a high spin state. The quenching experiments and EPR tests proved that the electro-Fenton system of FeN 6 /CN achieved high selectivity generation of 1 O 2 , showing excellent degradation performance of different organic pollutants. Combined with theoretical calculations, the FeN 6 sites displayed a lower energy barrier for the transfer from *H 2 O 2 to 1 O 2 . In the FeN 6 /CN’s electro-Fenton system, the high spin state of FeN 6 site ensured generation of H 2 O 2 via 2e - reduction. Simultaneously, the high oxidation state of FeN 6 site further achieved a highly selective generation of 1 O 2 by in situ activation of H 2 O 2 in the electro-Fenton system. Particularly, the FeN 6 /CN’s electro-Fenton system showed a high energy-efficient for pollutant removal (23.79 kWh·kg toc −1 ) compared to other electro-Fenton systems (50–300 kWh·kg toc −1 ). The electronic structure regulation of single atom sites provides a new avenue for highly selective generation of 1 O 2 in the electro-Fenton system.